Compiler exceptions

Src/AST/Myc.Ast.Compiler.Binder.pas

@@ -267,6 +267,10 @@ begin
     if not IsValidIdentifier(identifier.Name) then
         raise EBinderException.CreateFmt('Invalid identifier name: "%s".', [identifier.Name]);
 
+    // Check if the identifier is already defined in the current scope builder to avoid Scope Asserts.
+    if FCurrentBuilder.FindSlot(identifier.Name) >= 0 then
+        raise EBinderException.CreateFmt('Variable "%s" is already defined in this scope.', [identifier.Name]);
+
     slot := FCurrentBuilder.Define(identifier.Name);
     addr := TResolvedAddress.Create(akLocalOrParent, 0, slot);
 
@@ -334,6 +338,10 @@ begin
         SetLength(newParams, Length(Node.Parameters));
         for i := 0 to High(Node.Parameters) do
         begin
+            // Parameter names must also be checked for uniqueness, though usually guaranteed by Parser/AST construction
+            if FCurrentBuilder.FindSlot(Node.Parameters[i].Name) >= 0 then
+                raise EBinderException.CreateFmt('Duplicate parameter name "%s".', [Node.Parameters[i].Name]);
+
             slot := FCurrentBuilder.Define(Node.Parameters[i].Name);
             addr := TResolvedAddress.Create(akLocalOrParent, 0, slot);